Bremmer told Business Insider the deal is "helpful" to keep diplomacy alive for at least a little while longer. But in the end, there are major problems with the deal. Some of its provisions, including all illegal groups disarming, will not likely be completed — and Russia will look to exploit that.

"A key problem is the disarming of illegal groups — from Moscow's perspective, that means Ukrainian paramilitary organizations too," Bremmer wrote in an email Friday morning.

One of the groups to which Bremmer is referring is the ultranationalist Right Sector. Its leader and presidential candidate Dmytro Yarosh told his supporters this week to mobilize and be "prepared to take decisive actions to protect the sovereignty and territorial integrity of Ukraine."

The Right Sector and other smaller, similar groups have refused the interim Ukrainian government's demands to lay down their arms. Pro-Russian separatists in eastern Ukraine also have not de-weaponized, and they said they will continue to remain in government buildings until the members of the interim Ukrainian government resigns.

"They've ignored Kiev's demands to put down their weapons," Bremmer said of groups like the Right Sector. "And the Ukrainian government is hard-pressed to push further given the losses they've already taken in Crimea and the East. But I can't imagine Moscow doing much with the groups in the southeast while armed Ukrainian groups elsewhere persist."

Bremmer said the deal is ultimately helpful in the short-term, since the U.S. and other Western allies are at an impasse over how to further punish and respond to Russian President Vladimir Putin. Further sanctions won't change how he looks at Ukraine or his behavior, and both the U.S. and European countries are not willing to provide "lethal" military support for Ukraine in the event of conflict.

The deal provides a path for Ukraine out of a Russian invasion. But it will also make its government much weaker ahead of the May 25 elections — so the question is how far it wants to proceed down this path.

"There's lot of reason to be skeptical of the deal," Bremmer said.

"In short, it's a deal that aims to weaken the Ukrainian government, perhaps to the point of collapse. That's a way out of civil war and Russian invasion. But it's not one that Kiev is going to find attractive."